1. Field of Invention
The present invention relates to a neutralizing agent for clostridium bacterial neurotoxins and a preparation method thereof, and in particular, relates to a clostridium bacterial neurotoxin-neutralizing agent which can be added to food without affecting its flavor, to neutralize clostridium bacterial neurotoxins and protect from poisoning, and a preparation method of the clostridium bacterial neurotoxin-neutralizing agent.
2. Related Art
Clostridium botulinum is known to be the bacterium responsible for the mass food poisoning caused by Izushi (fermented Japanese food made from a mixture of fish, rice and vegetables) or Karashi-renkon (fried Japanese food made from lotus root) in the past in Japan, and also caused by ham, bottled food, etc. in the U.S. and Europe. This food poisoning is toxicosis due to oral intake of neurotoxins produced by the bacterium in food, rather than botulinum infection. Botulinum neurotoxin produced by botulinum is known to be the most potent neurotoxin to mammals owing to its high lethality. The neurotoxins are classified serologically into seven types (BoNT/A to G), and the process of the toxic action consists of the following three steps:
1) Binding of the toxic protein to the cell surface of presynaptic nerve terminal;
2) Internalization into cells; and
3) Proteolysis of the target protein by an endopeptidase activity present in the proteolytic domain.
Botulism can be treated with an antiserum therapy by administration of the antiserum. However, it is desirable to prevent before being affected by the poisoning, and the current method for prevention of the poisoning is to inhibit the bacterial growth and proliferation by means of sterilization of food by heating.
On the other hand, food that has been confirmed for the occurrence of botulism includes processed food such as ham, vacuum-packed food or bottled food, “Narezushi” (lactic acid fermented Japanese food) such as Izushi or Funazushi (a kind of fermented sushi made with fresh water fish), and the like, and it is obvious that there are difficult cases where sufficient sterilization can not be assured by heat sterilization. Therefore, search for substances to neutralize the neurotoxins is being conducted.
Under the above circumstances, it has become apparent that black tea extract contains botulinum neurotoxin-neutralizing substances, which have been found to be present in thearubigin fraction obtained by crude fractionation of black tea extract (refer to the references (1) and (2) below).
(1) Satoh E, Ishii T, Shimizu Y, Sawamura S and Nishimura M, “Black tea extract, thearubigin fraction, counteract the effects of botulinum neurotoxins in mice”, Br. J. Pharmacol., 132, 797-798(2001)
(2) Satoh E, Ishii T, Shimizu Y, Sawamura S and Nishimura M, “The mechanism underlying the protective effect of the thearubigin fraction of black tea (Camellia sinensis) extract against the neuromuscular blocking action of botulinum neurotoxins”, Pharmacol Toxicol, 90, 199-202(2002)
Thearubigin in black tea is a generic name for brown-colored acidic pigments fraction of black tea extract, which contains many substances besides those neutralizing the toxin and is effective in respect of neutralizing botulinum neurotoxins by being added to food.
However, when the thearubigin fraction of black tea is added to raw ham and the like, protein coagulation is brought about, showing “distasteful”, “astringent” and “bitter” tastes in the organoleptic test. Accordingly, it is necessary to identify the toxin-neutralizing substances in the thearubigin fraction of black tea and to purify the thearubigin fraction so as not to damage the flavor of food.